ADC08B3000 datasheet(13/32 Pages) NSC

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Specification Definitions (Continued)

GAIN ERROR is the deviation from the ideal slope of the

transfer function. It can be calculated from Offset and Full-

Scale Errors:

Positive Gain Error = Offset Error − Positive Full-Scale

Error

Negative Gain Error = −(Offset Error − Negative Full-

Scale Error)

Gain Error = Negative Full-Scale Error − Positive Full-

Scale Error = Positive Gain Error + Negative Gain Error

INTEGRAL NON-LINEARITY (INL) is a measure of the

deviation of each individual code from a straight line through

the input to output transfer function. The deviation of any

given code from this straight line is measured from the

center of that code value. The best fit method is used.

INTERMODULATION DISTORTION (IMD) is the creation of

additional spectral components as a result of two sinusoidal

frequencies being applied to the ADC input at the same time.

It is defined as the ratio of the power in the second and third

order intermodulation products to the power in one of the

original frequencies. IMD is usually expressed in dBFS.

LSB (LEAST SIGNIFICANT BIT) is the bit that has the

smallest value or weight of all bits. This value is

FS /2

where V

FS is the differential full-scale amplitude of 600 mV

or 800 mV as set by the FSR input and "n" is the ADC

resolution in bits, which is 8 for the ADC08B3000.

MISSING CODES are those output codes that are skipped

and will never appear at the ADC outputs. These codes

cannot be reached with any input value.

MSB (MOST SIGNIFICANT BIT) is the bit that has the

largest value or weight. Its value is one half of full scale.

NEGATIVE FULL-SCALE ERROR (NFSE) is a measure of

how far the last code transition is from the ideal 1/2 LSB

above a differential −435 mV with the FSR pin high, or 1/2

LSB above a differential −325 mV with the FSR pin low. For

the ADC08B3000 the reference voltage is assumed to be

ideal, so this error is a combination of full-scale error and

reference voltage error.

OFFSET ERROR (V

OFF) is a measure of how far the mid-

scale point is from the ideal zero voltage differential input.

Offset Error = Actual Input causing average of 8k

samples to result in an average code of 127.5.

OUTPUT DELAY (t

OD) is the time delay after the falling edge

of DRDY before the data update is present at the output

pins.

OVER-RANGE RECOVERY TIME is the time required after

the differential input voltages goes from ±1.2V to 0V for the

converter to recover and make a conversion with its rated

accuracy.

PIPELINE DELAY (LATENCY) is the number of input clock

cycles between initiation of conversion and when that data is

presented to the output driver stage. New data is available at

every clock cycle, but the data lags the conversion by the

Pipeline Delay plus the t

OD.

POSITIVE FULL-SCALE ERROR (PFSE) is a measure of

how far the last code transition is from the ideal 1-1/2 LSB

below a differential +435 mV with the FSR pin high, or 1-1/2

LSB below a differential +325 mV with the FSR pin low. For

the ADC08B3000 the reference voltage is assumed to be

ideal, so this error is a combination of full-scale error and

reference voltage error.

POWER SUPPLY REJECTION RATIO (PSRR) can be one

of two specifications. PSRR1 (DC PSRR) is the ratio of the

change in full-scale error that results from a power supply

voltage change from 1.8V to 2.0V. PSRR2 (AC PSRR) is a

measure of how well an a.c. signal riding upon the power

supply is rejected from the output and is measured with a

248 MHz, 50 mV

P-P signal riding upon the power supply. It is

the ratio of the output amplitude of that signal at the output to

its amplitude on the power supply pin. PSRR is expressed in

dB.

SIGNAL TO NOISE RATIO (SNR) is the ratio, expressed in

dB, of the rms value of the input signal at the output to the

rms value of the sum of all other spectral components below

one-half the sampling frequency, not including harmonics or

d.c.

SIGNAL TO NOISE PLUS DISTORTION (S/(N+D) or SI-

NAD) is the ratio, expressed in dB, of the rms value of the

input signal at the output to the rms value of all of the other

spectral components below half the input clock frequency,

including harmonics but excluding d.c.

SPURIOUS-FREE DYNAMIC RANGE (SFDR) is the differ-

ence, expressed in dB, between the rms values of the input

signal at the output and the peak spurious signal, where a

spurious signal is any signal present in the output spectrum

that is not present at the input, excluding d.c.

TOTAL HARMONIC DISTORTION (THD) is the ratio ex-

pressed in dB, of the rms total of the first nine harmonic

levels at the output to the level of the fundamental at the

output. THD is calculated as

where A

f1 is the RMS power of the fundamental (output)

frequency and A

f2 through Af10 are the RMS power of the

first 9 harmonic frequencies in the output spectrum.

– Second Harmonic Distortion (2nd Harm) is the differ-

ence, expressed in dB, between the RMS power in the input

frequency seen at the output and the power in its 2nd

harmonic level at the output.

– Third Harmonic Distortion (3rd Harm) is the difference

expressed in dB between the RMS power in the input fre-

quency seen at the output and the power in its 3rd harmonic

level at the output.

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